How does Atticus' opinion of Mrs. Dubose fit in with his defense of Tom Robinson?
Atticus explains to the children why he thinks Mrs. Duboe is a "great lady" and a brave soul. How does this fit with his explanation of why he is defending Tom Robinson?
Your question is a perfect one to connect to the theme associated with the title. "The Mockingbird" that it is a sin to kill symbolizes the person who is defenseless, who is "killed" either literally or symbolically by society. Atticus is the great defender of the the mockingbirds or the defenseless souls in the novel. Mrs. Dubose was a victim of society because soceity tends to label people as mean or spiteful without knowing what internal demons they are fighting. She was fighting a drug problem the hard way, by quitting on her own. Yet, no one except Atticus bothered to consider this. This proved that she was brave and a good person. Like Mrs. Dubose, Tom was also defenseless. Atticus knew that he wouldn't win the case, but he defended Tom to the best of his ability even though the town made him and his children miserable because of it. He did it for the same reason that he made Jem read to Mrs. Dubose, because they were victims of society who had no one else to defend them. Because Tom was black, society convicted him before he ever stepped into the courtroom. Even after Atticus proved he could never have hurt Mayella, the jury still sentenced Tom to death. Like the mockingbird, they had no chance of surviving in an unjust world.
I think that Atticus's decision to defend Tom Robinson makes a great deal of sense in conjunction with what Atticus says about Mrs. Dubose. His reasons for saying that she is a "great lady" are very similar, I think, to his reasons for defending Robinson.
To me, the crucial quote is this one. Atticus is talking about why Mrs. Dubose is "great." He says that being great is
...when you know you're licked before you begin but you begin anyway and you see it through no matter what.
If you think about it, this is exactly what Atticus is doing when he takes on the Tom Robinson case. He has to know that he's never going to get Tom acquitted, but he takes the case anyway and he fights as hard as he possibly can to try to win it (even though he loses in the end).
I wanted you to see what real courage is, instead of getting the idea that courage is a man with a gun in his hand. It's when you know you're licked before you begin but you begin anyway and you see it through no matter what. You rarely win, but sometimes you do. Mrs Dubose won, all ninety-eight pounds of her. According to her views, she died beholden to nothing and nobody. She was the bravest person I ever knew.'
This is the quote Atticus uses to explain to the children why Mrs. Dubose is heroic. In the story Mrs. Dubose wants to fight her addiction to morphine before she passes away. Many people see her as a mean old lady; however, she is determined to die on her own terms remaining true to her own conscious.
Another famous quote in the book from Atticus is, "The one thing that doesn't abide by majority rule is a person's conscience."
Mrs. Dubose knows in the novel she is dying and that by not taking the morphine, not only is her own death imminent, but she will die in pain. In the same way Atticus knows he is going to lose the trial of Tom Robinson and face ridicule and judgement from many people in town. Both characters though know, ultimately, the most important person they need to answer to is himself/herself. Neither Atticus or Mrs. Dubose could live or die courageously or justly with another decision than the one they made.
The reason he takes up Tom's case is for justice. He is a man who believes in strong morals and even though he would get shunned for taking the side of an African man, he did not care because he wanted to make sure that proper justice was given to him.